/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2005 Blender Foundation.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): Brecht Van Lommel.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/gpu/intern/gpu_buffers.c
 *  \ingroup gpu
 */


#include <limits.h>
#include <stddef.h>
#include <string.h>

#include "GL/glew.h"

#include "MEM_guardedalloc.h"

#include "BLI_bitmap.h"
#include "BLI_math.h"
#include "BLI_utildefines.h"
#include "BLI_ghash.h"
#include "BLI_threads.h"

#include "DNA_meshdata_types.h"

#include "BKE_DerivedMesh.h"
#include "BKE_paint.h"
#include "BKE_subsurf.h"

#include "DNA_userdef_types.h"

#include "GPU_buffers.h"

typedef enum {
	GPU_BUFFER_VERTEX_STATE = 1,
	GPU_BUFFER_NORMAL_STATE = 2,
	GPU_BUFFER_TEXCOORD_STATE = 4,
	GPU_BUFFER_COLOR_STATE = 8,
	GPU_BUFFER_ELEMENT_STATE = 16,
} GPUBufferState;

#define MAX_GPU_ATTRIB_DATA 32

/* material number is an 16-bit short and the range of short is from -16383 to 16383 (assume material number is non-negative) */
#define MAX_MATERIALS 16384

/* -1 - undefined, 0 - vertex arrays, 1 - VBOs */
static int useVBOs = -1;
static GPUBufferState GLStates = 0;
static GPUAttrib attribData[MAX_GPU_ATTRIB_DATA] = { { -1, 0, 0 } };

/* stores recently-deleted buffers so that new buffers won't have to
 * be recreated as often
 *
 * only one instance of this pool is created, stored in
 * gpu_buffer_pool
 *
 * note that the number of buffers in the pool is usually limited to
 * MAX_FREE_GPU_BUFFERS, but this limit may be exceeded temporarily
 * when a GPUBuffer is released outside the main thread; due to OpenGL
 * restrictions it cannot be immediately released
 */
typedef struct GPUBufferPool {
	/* number of allocated buffers stored */
	int totbuf;
	/* actual allocated length of the array */
	int maxsize;
	GPUBuffer **buffers;
} GPUBufferPool;
#define MAX_FREE_GPU_BUFFERS 8

/* create a new GPUBufferPool */
static GPUBufferPool *gpu_buffer_pool_new(void)
{
	GPUBufferPool *pool;

	/* enable VBOs if supported */
	if (useVBOs == -1)
		useVBOs = (GLEW_ARB_vertex_buffer_object ? 1 : 0);

	pool = MEM_callocN(sizeof(GPUBufferPool), "GPUBuffer");

	pool->maxsize = MAX_FREE_GPU_BUFFERS;
	pool->buffers = MEM_callocN(sizeof(GPUBuffer*)*pool->maxsize,
				    "GPUBuffer.buffers");

	return pool;
}

/* remove a GPUBuffer from the pool (does not free the GPUBuffer) */
static void gpu_buffer_pool_remove_index(GPUBufferPool *pool, int index)
{
	int i;

	if (!pool || index < 0 || index >= pool->totbuf)
		return;

	/* shift entries down, overwriting the buffer at `index' */
	for (i = index; i < pool->totbuf - 1; i++)
		pool->buffers[i] = pool->buffers[i+1];

	/* clear the last entry */
	if (pool->totbuf > 0)
		pool->buffers[pool->totbuf - 1] = NULL;

	pool->totbuf--;
}

/* delete the last entry in the pool */
static void gpu_buffer_pool_delete_last(GPUBufferPool *pool)
{
	GPUBuffer *last;

	if (pool->totbuf <= 0)
		return;

	/* get the last entry */
	if (!(last = pool->buffers[pool->totbuf - 1]))
		return;

	/* delete the buffer's data */
	if (useVBOs)
		glDeleteBuffersARB(1, &last->id);
	else
		MEM_freeN(last->pointer);

	/* delete the buffer and remove from pool */
	MEM_freeN(last);
	pool->totbuf--;
	pool->buffers[pool->totbuf] = NULL;
}

/* free a GPUBufferPool; also frees the data in the pool's
 * GPUBuffers */
static void gpu_buffer_pool_free(GPUBufferPool *pool)
{
	if (!pool)
		return;
	
	while (pool->totbuf)
		gpu_buffer_pool_delete_last(pool);

	MEM_freeN(pool->buffers);
	MEM_freeN(pool);
}

static GPUBufferPool *gpu_buffer_pool = NULL;
static GPUBufferPool *gpu_get_global_buffer_pool(void)
{
	/* initialize the pool */
	if (!gpu_buffer_pool)
		gpu_buffer_pool = gpu_buffer_pool_new();

	return gpu_buffer_pool;
}

void GPU_global_buffer_pool_free(void)
{
	gpu_buffer_pool_free(gpu_buffer_pool);
	gpu_buffer_pool = NULL;
}

/* get a GPUBuffer of at least `size' bytes; uses one from the buffer
 * pool if possible, otherwise creates a new one */
GPUBuffer *GPU_buffer_alloc(int size)
{
	GPUBufferPool *pool;
	GPUBuffer *buf;
	int i, bufsize, bestfit = -1;

	pool = gpu_get_global_buffer_pool();

	/* not sure if this buffer pool code has been profiled much,
	 * seems to me that the graphics driver and system memory
	 * management might do this stuff anyway. --nicholas
	 */

	/* check the global buffer pool for a recently-deleted buffer
	 * that is at least as big as the request, but not more than
	 * twice as big */
	for (i = 0; i < pool->totbuf; i++) {
		bufsize = pool->buffers[i]->size;

		/* check for an exact size match */
		if (bufsize == size) {
			bestfit = i;
			break;
		}
		/* smaller buffers won't fit data and buffers at least
		 * twice as big are a waste of memory */
		else if (bufsize > size && size > (bufsize / 2)) {
			/* is it closer to the required size than the
			 * last appropriate buffer found. try to save
			 * memory */
			if (bestfit == -1 || pool->buffers[bestfit]->size > bufsize) {
				bestfit = i;
			}
		}
	}

	/* if an acceptable buffer was found in the pool, remove it
	 * from the pool and return it */
	if (bestfit != -1) {
		buf = pool->buffers[bestfit];
		gpu_buffer_pool_remove_index(pool, bestfit);
		return buf;
	}

	/* no acceptable buffer found in the pool, create a new one */
	buf = MEM_callocN(sizeof(GPUBuffer), "GPUBuffer");
	buf->size = size;

	if (useVBOs == 1) {
		/* create a new VBO and initialize it to the requested
		 * size */
		glGenBuffersARB(1, &buf->id);
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buf->id);
		glBufferDataARB(GL_ARRAY_BUFFER_ARB, size, NULL, GL_STATIC_DRAW_ARB);
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
	}
	else {
		buf->pointer = MEM_mallocN(size, "GPUBuffer.pointer");
		
		/* purpose of this seems to be dealing with
		 * out-of-memory errors? looks a bit iffy to me
		 * though, at least on Linux I expect malloc() would
		 * just overcommit. --nicholas */
		while (!buf->pointer && pool->totbuf > 0) {
			gpu_buffer_pool_delete_last(pool);
			buf->pointer = MEM_mallocN(size, "GPUBuffer.pointer");
		}
		if (!buf->pointer)
			return NULL;
	}

	return buf;
}

/* release a GPUBuffer; does not free the actual buffer or its data,
 * but rather moves it to the pool of recently-freed buffers for
 * possible re-use*/
void GPU_buffer_free(GPUBuffer *buffer)
{
	GPUBufferPool *pool;
	int i;

	if (!buffer)
		return;

	pool = gpu_get_global_buffer_pool();

	/* free the last used buffer in the queue if no more space, but only
	 * if we are in the main thread. for e.g. rendering or baking it can
	 * happen that we are in other thread and can't call OpenGL, in that
	 * case cleanup will be done GPU_buffer_pool_free_unused */
	if (BLI_thread_is_main()) {
		/* in main thread, safe to decrease size of pool back
		 * down to MAX_FREE_GPU_BUFFERS */
		while (pool->totbuf >= MAX_FREE_GPU_BUFFERS)
			gpu_buffer_pool_delete_last(pool);
	}
	else {
		/* outside of main thread, can't safely delete the
		 * buffer, so increase pool size */
		if (pool->maxsize == pool->totbuf) {
			pool->maxsize += MAX_FREE_GPU_BUFFERS;
			pool->buffers = MEM_reallocN(pool->buffers,
						     sizeof(GPUBuffer*) * pool->maxsize);
		}
	}

	/* shift pool entries up by one */
	for (i = pool->totbuf; i > 0; i--)
		pool->buffers[i] = pool->buffers[i-1];

	/* insert the buffer into the beginning of the pool */
	pool->buffers[0] = buffer;
	pool->totbuf++;
}

typedef struct GPUVertPointLink {
	struct GPUVertPointLink *next;
	/* -1 means uninitialized */
	int point_index;
} GPUVertPointLink;

/* add a new point to the list of points related to a particular
 * vertex */
static void gpu_drawobject_add_vert_point(GPUDrawObject *gdo, int vert_index, int point_index)
{
	GPUVertPointLink *lnk;

	lnk = &gdo->vert_points[vert_index];

	/* if first link is in use, add a new link at the end */
	if (lnk->point_index != -1) {
		/* get last link */
		for (; lnk->next; lnk = lnk->next);

		/* add a new link from the pool */
		lnk = lnk->next = &gdo->vert_points_mem[gdo->vert_points_usage];
		gdo->vert_points_usage++;
	}

	lnk->point_index = point_index;
}

/* update the vert_points and triangle_to_mface fields with a new
 * triangle */
static void gpu_drawobject_add_triangle(GPUDrawObject *gdo,
					int base_point_index,
					int face_index,
					int v1, int v2, int v3)
{
	int i, v[3] = {v1, v2, v3};
	for (i = 0; i < 3; i++)
		gpu_drawobject_add_vert_point(gdo, v[i], base_point_index + i);
	gdo->triangle_to_mface[base_point_index / 3] = face_index;
}

/* for each vertex, build a list of points related to it; these lists
 * are stored in an array sized to the number of vertices */
static void gpu_drawobject_init_vert_points(GPUDrawObject *gdo, MFace *f, int totface)
{
	GPUBufferMaterial *mat;
	int i, mat_orig_to_new[MAX_MATERIALS];

	/* allocate the array and space for links */
	gdo->vert_points = MEM_callocN(sizeof(GPUVertPointLink) * gdo->totvert,
				       "GPUDrawObject.vert_points");
	gdo->vert_points_mem = MEM_callocN(sizeof(GPUVertPointLink) * gdo->tot_triangle_point,
					      "GPUDrawObject.vert_points_mem");
	gdo->vert_points_usage = 0;

	/* build a map from the original material indices to the new
	 * GPUBufferMaterial indices */
	for (i = 0; i < gdo->totmaterial; i++)
		mat_orig_to_new[gdo->materials[i].mat_nr] = i;

	/* -1 indicates the link is not yet used */
	for (i = 0; i < gdo->totvert; i++)
		gdo->vert_points[i].point_index = -1;

	for (i = 0; i < totface; i++, f++) {
		mat = &gdo->materials[mat_orig_to_new[f->mat_nr]];

		/* add triangle */
		gpu_drawobject_add_triangle(gdo, mat->start + mat->totpoint,
					    i, f->v1, f->v2, f->v3);
		mat->totpoint += 3;

		/* add second triangle for quads */
		if (f->v4) {
			gpu_drawobject_add_triangle(gdo, mat->start + mat->totpoint,
						    i, f->v3, f->v4, f->v1);
			mat->totpoint += 3;
		}
	}

	/* map any unused vertices to loose points */
	for (i = 0; i < gdo->totvert; i++) {
		if (gdo->vert_points[i].point_index == -1) {
			gdo->vert_points[i].point_index = gdo->tot_triangle_point + gdo->tot_loose_point;
			gdo->tot_loose_point++;
		}
	}
}

/* see GPUDrawObject's structure definition for a description of the
 * data being initialized here */
GPUDrawObject *GPU_drawobject_new( DerivedMesh *dm )
{
	GPUDrawObject *gdo;
	MFace *mface;
	int points_per_mat[MAX_MATERIALS];
	int i, curmat, curpoint, totface;

	mface = dm->getTessFaceArray(dm);
	totface= dm->getNumTessFaces(dm);

	/* get the number of points used by each material, treating
	 * each quad as two triangles */
	memset(points_per_mat, 0, sizeof(int)*MAX_MATERIALS);
	for (i = 0; i < totface; i++)
		points_per_mat[mface[i].mat_nr] += mface[i].v4 ? 6 : 3;

	/* create the GPUDrawObject */
	gdo = MEM_callocN(sizeof(GPUDrawObject),"GPUDrawObject");
	gdo->totvert = dm->getNumVerts(dm);
	gdo->totedge = dm->getNumEdges(dm);

	/* count the number of materials used by this DerivedMesh */
	for (i = 0; i < MAX_MATERIALS; i++) {
		if (points_per_mat[i] > 0)
			gdo->totmaterial++;
	}

	/* allocate an array of materials used by this DerivedMesh */
	gdo->materials = MEM_mallocN(sizeof(GPUBufferMaterial) * gdo->totmaterial,
				     "GPUDrawObject.materials");

	/* initialize the materials array */
	for (i = 0, curmat = 0, curpoint = 0; i < MAX_MATERIALS; i++) {
		if (points_per_mat[i] > 0) {
			gdo->materials[curmat].start = curpoint;
			gdo->materials[curmat].totpoint = 0;
			gdo->materials[curmat].mat_nr = i;

			curpoint += points_per_mat[i];
			curmat++;
		}
	}

	/* store total number of points used for triangles */
	gdo->tot_triangle_point = curpoint;

	gdo->triangle_to_mface = MEM_mallocN(sizeof(int) * (gdo->tot_triangle_point / 3),
				     "GPUDrawObject.triangle_to_mface");

	gpu_drawobject_init_vert_points(gdo, mface, totface);

	return gdo;
}

void GPU_drawobject_free(DerivedMesh *dm)
{
	GPUDrawObject *gdo;

	if (!dm || !(gdo = dm->drawObject))
		return;

	MEM_freeN(gdo->materials);
	MEM_freeN(gdo->triangle_to_mface);
	MEM_freeN(gdo->vert_points);
	MEM_freeN(gdo->vert_points_mem);
	GPU_buffer_free(gdo->points);
	GPU_buffer_free(gdo->normals);
	GPU_buffer_free(gdo->uv);
	GPU_buffer_free(gdo->colors);
	GPU_buffer_free(gdo->edges);
	GPU_buffer_free(gdo->uvedges);

	MEM_freeN(gdo);
	dm->drawObject = NULL;
}

typedef void (*GPUBufferCopyFunc)(DerivedMesh *dm, float *varray, int *index,
                                  int *mat_orig_to_new, void *user_data);

static GPUBuffer *gpu_buffer_setup(DerivedMesh *dm, GPUDrawObject *object,
                                   int vector_size, int size, GLenum target,
                                   void *user, GPUBufferCopyFunc copy_f)
{
	GPUBufferPool *pool;
	GPUBuffer *buffer;
	float *varray;
	int mat_orig_to_new[MAX_MATERIALS];
	int *cur_index_per_mat;
	int i;
	int success;
	GLboolean uploaded;

	pool = gpu_get_global_buffer_pool();

	/* alloc a GPUBuffer; fall back to legacy mode on failure */
	if (!(buffer = GPU_buffer_alloc(size)))
		dm->drawObject->legacy = 1;

	/* nothing to do for legacy mode */
	if (dm->drawObject->legacy)
		return NULL;

	cur_index_per_mat = MEM_mallocN(sizeof(int)*object->totmaterial,
					"GPU_buffer_setup.cur_index_per_mat");
	for (i = 0; i < object->totmaterial; i++) {
		/* for each material, the current index to copy data to */
		cur_index_per_mat[i] = object->materials[i].start * vector_size;

		/* map from original material index to new
		 * GPUBufferMaterial index */
		mat_orig_to_new[object->materials[i].mat_nr] = i;
	}

	if (useVBOs) {
		success = 0;

		while (!success) {
			/* bind the buffer and discard previous data,
			 * avoids stalling gpu */
			glBindBufferARB(target, buffer->id);
			glBufferDataARB(target, buffer->size, NULL, GL_STATIC_DRAW_ARB);

			/* attempt to map the buffer */
			if (!(varray = glMapBufferARB(target, GL_WRITE_ONLY_ARB))) {
				/* failed to map the buffer; delete it */
				GPU_buffer_free(buffer);
				gpu_buffer_pool_delete_last(pool);
				buffer= NULL;

				/* try freeing an entry from the pool
				 * and reallocating the buffer */
				if (pool->totbuf > 0) {
					gpu_buffer_pool_delete_last(pool);
					buffer = GPU_buffer_alloc(size);
				}

				/* allocation still failed; fall back
				 * to legacy mode */
				if (!buffer) {
					dm->drawObject->legacy = 1;
					success = 1;
				}
			}
			else {
				success = 1;
			}
		}

		/* check legacy fallback didn't happen */
		if (dm->drawObject->legacy == 0) {
			uploaded = GL_FALSE;
			/* attempt to upload the data to the VBO */
			while (uploaded == GL_FALSE) {
				(*copy_f)(dm, varray, cur_index_per_mat, mat_orig_to_new, user);
				/* glUnmapBuffer returns GL_FALSE if
				 * the data store is corrupted; retry
				 * in that case */
				uploaded = glUnmapBufferARB(target);
			}
		}
		glBindBufferARB(target, 0);
	}
	else {
		/* VBO not supported, use vertex array fallback */
		if (buffer->pointer) {
			varray = buffer->pointer;
			(*copy_f)(dm, varray, cur_index_per_mat, mat_orig_to_new, user);
		}
		else {
			dm->drawObject->legacy = 1;
		}
	}

	MEM_freeN(cur_index_per_mat);

	return buffer;
}

static void GPU_buffer_copy_vertex(DerivedMesh *dm, float *varray, int *index, int *mat_orig_to_new, void *UNUSED(user))
{
	MVert *mvert;
	MFace *f;
	int i, j, start, totface;

	mvert = dm->getVertArray(dm);
	f = dm->getTessFaceArray(dm);

	totface= dm->getNumTessFaces(dm);
	for (i = 0; i < totface; i++, f++) {
		start = index[mat_orig_to_new[f->mat_nr]];

		/* v1 v2 v3 */
		copy_v3_v3(&varray[start], mvert[f->v1].co);
		copy_v3_v3(&varray[start+3], mvert[f->v2].co);
		copy_v3_v3(&varray[start+6], mvert[f->v3].co);
		index[mat_orig_to_new[f->mat_nr]] += 9;

		if (f->v4) {
			/* v3 v4 v1 */
			copy_v3_v3(&varray[start+9], mvert[f->v3].co);
			copy_v3_v3(&varray[start+12], mvert[f->v4].co);
			copy_v3_v3(&varray[start+15], mvert[f->v1].co);
			index[mat_orig_to_new[f->mat_nr]] += 9;
		}
	}

	/* copy loose points */
	j = dm->drawObject->tot_triangle_point*3;
	for (i = 0; i < dm->drawObject->totvert; i++) {
		if (dm->drawObject->vert_points[i].point_index >= dm->drawObject->tot_triangle_point) {
			copy_v3_v3(&varray[j],mvert[i].co);
			j+=3;
		}
	}
}

static void GPU_buffer_copy_normal(DerivedMesh *dm, float *varray, int *index, int *mat_orig_to_new, void *UNUSED(user))
{
	int i, totface;
	int start;
	float f_no[3];

	float *nors= dm->getTessFaceDataArray(dm, CD_NORMAL);
	MVert *mvert = dm->getVertArray(dm);
	MFace *f = dm->getTessFaceArray(dm);

	totface= dm->getNumTessFaces(dm);
	for (i = 0; i < totface; i++, f++) {
		const int smoothnormal = (f->flag & ME_SMOOTH);

		start = index[mat_orig_to_new[f->mat_nr]];
		index[mat_orig_to_new[f->mat_nr]] += f->v4 ? 18 : 9;

		if (smoothnormal) {
			/* copy vertex normal */
			normal_short_to_float_v3(&varray[start], mvert[f->v1].no);
			normal_short_to_float_v3(&varray[start+3], mvert[f->v2].no);
			normal_short_to_float_v3(&varray[start+6], mvert[f->v3].no);

			if (f->v4) {
				normal_short_to_float_v3(&varray[start+9], mvert[f->v3].no);
				normal_short_to_float_v3(&varray[start+12], mvert[f->v4].no);
				normal_short_to_float_v3(&varray[start+15], mvert[f->v1].no);
			}
		}
		else if (nors) {
			/* copy cached face normal */
			copy_v3_v3(&varray[start], &nors[i*3]);
			copy_v3_v3(&varray[start+3], &nors[i*3]);
			copy_v3_v3(&varray[start+6], &nors[i*3]);

			if (f->v4) {
				copy_v3_v3(&varray[start+9], &nors[i*3]);
				copy_v3_v3(&varray[start+12], &nors[i*3]);
				copy_v3_v3(&varray[start+15], &nors[i*3]);
			}
		}
		else {
			/* calculate face normal */
			if (f->v4)
				normal_quad_v3(f_no, mvert[f->v1].co, mvert[f->v2].co, mvert[f->v3].co, mvert[f->v4].co);
			else
				normal_tri_v3(f_no, mvert[f->v1].co, mvert[f->v2].co, mvert[f->v3].co);

			copy_v3_v3(&varray[start], f_no);
			copy_v3_v3(&varray[start+3], f_no);
			copy_v3_v3(&varray[start+6], f_no);

			if (f->v4) {
				copy_v3_v3(&varray[start+9], f_no);
				copy_v3_v3(&varray[start+12], f_no);
				copy_v3_v3(&varray[start+15], f_no);
			}
		}
	}
}

static void GPU_buffer_copy_uv(DerivedMesh *dm, float *varray, int *index, int *mat_orig_to_new, void *UNUSED(user))
{
	int start;
	int i, totface;

	MTFace *mtface;
	MFace *f;

	if (!(mtface = DM_get_tessface_data_layer(dm, CD_MTFACE)))
		return;
	f = dm->getTessFaceArray(dm);
		
	totface = dm->getNumTessFaces(dm);
	for (i = 0; i < totface; i++, f++) {
		start = index[mat_orig_to_new[f->mat_nr]];

		/* v1 v2 v3 */
		copy_v2_v2(&varray[start],mtface[i].uv[0]);
		copy_v2_v2(&varray[start+2],mtface[i].uv[1]);
		copy_v2_v2(&varray[start+4],mtface[i].uv[2]);
		index[mat_orig_to_new[f->mat_nr]] += 6;

		if (f->v4) {
			/* v3 v4 v1 */
			copy_v2_v2(&varray[start+6],mtface[i].uv[2]);
			copy_v2_v2(&varray[start+8],mtface[i].uv[3]);
			copy_v2_v2(&varray[start+10],mtface[i].uv[0]);
			index[mat_orig_to_new[f->mat_nr]] += 6;
		}
	}
}


static void GPU_buffer_copy_color3(DerivedMesh *dm, float *varray_, int *index, int *mat_orig_to_new, void *user)
{
	int i, totface;
	char *varray = (char *)varray_;
	char *mcol = (char *)user;
	MFace *f = dm->getTessFaceArray(dm);

	totface= dm->getNumTessFaces(dm);
	for (i=0; i < totface; i++, f++) {
		int start = index[mat_orig_to_new[f->mat_nr]];

		/* v1 v2 v3 */
		copy_v3_v3_char(&varray[start], &mcol[i*12]);
		copy_v3_v3_char(&varray[start+3], &mcol[i*12+3]);
		copy_v3_v3_char(&varray[start+6], &mcol[i*12+6]);
		index[mat_orig_to_new[f->mat_nr]] += 9;

		if (f->v4) {
			/* v3 v4 v1 */
			copy_v3_v3_char(&varray[start+9], &mcol[i*12+6]);
			copy_v3_v3_char(&varray[start+12], &mcol[i*12+9]);
			copy_v3_v3_char(&varray[start+15], &mcol[i*12]);
			index[mat_orig_to_new[f->mat_nr]] += 9;
		}
	}
}

static void copy_mcol_uc3(unsigned char *v, unsigned char *col)
{
	v[0] = col[3];
	v[1] = col[2];
	v[2] = col[1];
}

/* treat varray_ as an array of MCol, four MCol's per face */
static void GPU_buffer_copy_mcol(DerivedMesh *dm, float *varray_, int *index, int *mat_orig_to_new, void *user)
{
	int i, totface;
	unsigned char *varray = (unsigned char *)varray_;
	unsigned char *mcol = (unsigned char *)user;
	MFace *f = dm->getTessFaceArray(dm);

	totface= dm->getNumTessFaces(dm);
	for (i=0; i < totface; i++, f++) {
		int start = index[mat_orig_to_new[f->mat_nr]];

		/* v1 v2 v3 */
		copy_mcol_uc3(&varray[start], &mcol[i*16]);
		copy_mcol_uc3(&varray[start+3], &mcol[i*16+4]);
		copy_mcol_uc3(&varray[start+6], &mcol[i*16+8]);
		index[mat_orig_to_new[f->mat_nr]] += 9;

		if (f->v4) {
			/* v3 v4 v1 */
			copy_mcol_uc3(&varray[start+9], &mcol[i*16+8]);
			copy_mcol_uc3(&varray[start+12], &mcol[i*16+12]);
			copy_mcol_uc3(&varray[start+15], &mcol[i*16]);
			index[mat_orig_to_new[f->mat_nr]] += 9;
		}
	}
}

static void GPU_buffer_copy_edge(DerivedMesh *dm, float *varray_, int *UNUSED(index), int *UNUSED(mat_orig_to_new), void *UNUSED(user))
{
	MEdge *medge;
	unsigned int *varray = (unsigned int *)varray_;
	int i, totedge;
 
	medge = dm->getEdgeArray(dm);
	totedge = dm->getNumEdges(dm);

	for (i = 0; i < totedge; i++, medge++) {
		varray[i*2] = dm->drawObject->vert_points[medge->v1].point_index;
		varray[i*2+1] = dm->drawObject->vert_points[medge->v2].point_index;
	}
}

static void GPU_buffer_copy_uvedge(DerivedMesh *dm, float *varray, int *UNUSED(index), int *UNUSED(mat_orig_to_new), void *UNUSED(user))
{
	MTFace *tf = DM_get_tessface_data_layer(dm, CD_MTFACE);
	int i, j=0;

	if (!tf)
		return;

	for (i = 0; i < dm->numTessFaceData; i++, tf++) {
		MFace mf;
		dm->getTessFace(dm,i,&mf);

		copy_v2_v2(&varray[j],tf->uv[0]);
		copy_v2_v2(&varray[j+2],tf->uv[1]);

		copy_v2_v2(&varray[j+4],tf->uv[1]);
		copy_v2_v2(&varray[j+6],tf->uv[2]);

		if (!mf.v4) {
			copy_v2_v2(&varray[j+8],tf->uv[2]);
			copy_v2_v2(&varray[j+10],tf->uv[0]);
			j+=12;
		}
		else {
			copy_v2_v2(&varray[j+8],tf->uv[2]);
			copy_v2_v2(&varray[j+10],tf->uv[3]);

			copy_v2_v2(&varray[j+12],tf->uv[3]);
			copy_v2_v2(&varray[j+14],tf->uv[0]);
			j+=16;
		}
	}
}

/* get the DerivedMesh's MCols; choose (in decreasing order of
 * preference) from CD_ID_MCOL, CD_PREVIEW_MCOL, or CD_MCOL */
static MCol *gpu_buffer_color_type(DerivedMesh *dm)
{
	MCol *c;
	int type;

	type = CD_ID_MCOL;
	c = DM_get_tessface_data_layer(dm, type);
	if (!c) {
		type = CD_PREVIEW_MCOL;
		c = DM_get_tessface_data_layer(dm, type);
		if (!c) {
			type = CD_MCOL;
			c = DM_get_tessface_data_layer(dm, type);
		}
	}

	dm->drawObject->colType = type;
	return c;
}

typedef enum {
	GPU_BUFFER_VERTEX = 0,
	GPU_BUFFER_NORMAL,
	GPU_BUFFER_COLOR,
	GPU_BUFFER_UV,
	GPU_BUFFER_EDGE,
	GPU_BUFFER_UVEDGE,
} GPUBufferType;

typedef struct {
	GPUBufferCopyFunc copy;
	GLenum gl_buffer_type;
	int vector_size;
} GPUBufferTypeSettings;

const GPUBufferTypeSettings gpu_buffer_type_settings[] = {
	{GPU_buffer_copy_vertex, GL_ARRAY_BUFFER_ARB, 3},
	{GPU_buffer_copy_normal, GL_ARRAY_BUFFER_ARB, 3},
	{GPU_buffer_copy_mcol, GL_ARRAY_BUFFER_ARB, 3},
	{GPU_buffer_copy_uv, GL_ARRAY_BUFFER_ARB, 2},
	{GPU_buffer_copy_edge, GL_ELEMENT_ARRAY_BUFFER_ARB, 2},
	{GPU_buffer_copy_uvedge, GL_ELEMENT_ARRAY_BUFFER_ARB, 4}
};

/* get the GPUDrawObject buffer associated with a type */
static GPUBuffer **gpu_drawobject_buffer_from_type(GPUDrawObject *gdo, GPUBufferType type)
{
	switch (type) {
	case GPU_BUFFER_VERTEX:
		return &gdo->points;
	case GPU_BUFFER_NORMAL:
		return &gdo->normals;
	case GPU_BUFFER_COLOR:
		return &gdo->colors;
	case GPU_BUFFER_UV:
		return &gdo->uv;
	case GPU_BUFFER_EDGE:
		return &gdo->edges;
	case GPU_BUFFER_UVEDGE:
		return &gdo->uvedges;
	default:
		return NULL;
	}
}

/* get the amount of space to allocate for a buffer of a particular type */
static int gpu_buffer_size_from_type(DerivedMesh *dm, GPUBufferType type)
{
	switch (type) {
	case GPU_BUFFER_VERTEX:
		return sizeof(float)*3 * (dm->drawObject->tot_triangle_point + dm->drawObject->tot_loose_point);
	case GPU_BUFFER_NORMAL:
		return sizeof(float)*3*dm->drawObject->tot_triangle_point;
	case GPU_BUFFER_COLOR:
		return sizeof(char)*3*dm->drawObject->tot_triangle_point;
	case GPU_BUFFER_UV:
		return sizeof(float)*2*dm->drawObject->tot_triangle_point;
	case GPU_BUFFER_EDGE:
		return sizeof(int)*2*dm->drawObject->totedge;
	case GPU_BUFFER_UVEDGE:
		/* each face gets 3 points, 3 edges per triangle, and
		 * each edge has its own, non-shared coords, so each
		 * tri corner needs minimum of 4 floats, quads used
		 * less so here we can over allocate and assume all
		 * tris. */
		return sizeof(float) * 4 * dm->drawObject->tot_triangle_point;
	default:
		return -1;
	}
}

/* call gpu_buffer_setup with settings for a particular type of buffer */
static GPUBuffer *gpu_buffer_setup_type(DerivedMesh *dm, GPUBufferType type)
{
	const GPUBufferTypeSettings *ts;
	void *user_data = NULL;
	GPUBuffer *buf;

	ts = &gpu_buffer_type_settings[type];

	/* special handling for MCol and UV buffers */
	if (type == GPU_BUFFER_COLOR) {
		if (!(user_data = gpu_buffer_color_type(dm)))
			return NULL;
	}
	else if (type == GPU_BUFFER_UV) {
		if (!DM_get_tessface_data_layer(dm, CD_MTFACE))
			return NULL;
	}

	buf = gpu_buffer_setup(dm, dm->drawObject, ts->vector_size,
	                       gpu_buffer_size_from_type(dm, type),
	                       ts->gl_buffer_type, user_data, ts->copy);

	return buf;
}

/* get the buffer of `type', initializing the GPUDrawObject and
 * buffer if needed */
static GPUBuffer *gpu_buffer_setup_common(DerivedMesh *dm, GPUBufferType type)
{
	GPUBuffer **buf;
	
	if (!dm->drawObject)
		dm->drawObject = GPU_drawobject_new(dm);

	buf = gpu_drawobject_buffer_from_type(dm->drawObject, type);
	if (!(*buf))
		*buf = gpu_buffer_setup_type(dm, type);

	return *buf;
}

void GPU_vertex_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_VERTEX))
		return;

	glEnableClientState(GL_VERTEX_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->points->id);
		glVertexPointer(3, GL_FLOAT, 0, 0);
	}
	else {
		glVertexPointer(3, GL_FLOAT, 0, dm->drawObject->points->pointer);
	}
	
	GLStates |= GPU_BUFFER_VERTEX_STATE;
}

void GPU_normal_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_NORMAL))
		return;

	glEnableClientState(GL_NORMAL_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->normals->id);
		glNormalPointer(GL_FLOAT, 0, 0);
	}
	else {
		glNormalPointer(GL_FLOAT, 0, dm->drawObject->normals->pointer);
	}

	GLStates |= GPU_BUFFER_NORMAL_STATE;
}

void GPU_uv_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_UV))
		return;

	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->uv->id);
		glTexCoordPointer(2, GL_FLOAT, 0, 0);
	}
	else {
		glTexCoordPointer(2, GL_FLOAT, 0, dm->drawObject->uv->pointer);
	}

	GLStates |= GPU_BUFFER_TEXCOORD_STATE;
}

void GPU_color_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_COLOR))
		return;

	glEnableClientState(GL_COLOR_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->colors->id);
		glColorPointer(3, GL_UNSIGNED_BYTE, 0, 0);
	}
	else {
		glColorPointer(3, GL_UNSIGNED_BYTE, 0, dm->drawObject->colors->pointer);
	}

	GLStates |= GPU_BUFFER_COLOR_STATE;
}

void GPU_edge_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_EDGE))
		return;

	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_VERTEX))
		return;

	glEnableClientState(GL_VERTEX_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->points->id);
		glVertexPointer(3, GL_FLOAT, 0, 0);
	}
	else {
		glVertexPointer(3, GL_FLOAT, 0, dm->drawObject->points->pointer);
	}
	
	GLStates |= GPU_BUFFER_VERTEX_STATE;

	if (useVBOs)
		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, dm->drawObject->edges->id);

	GLStates |= GPU_BUFFER_ELEMENT_STATE;
}

void GPU_uvedge_setup(DerivedMesh *dm)
{
	if (!gpu_buffer_setup_common(dm, GPU_BUFFER_UVEDGE))
		return;

	glEnableClientState(GL_VERTEX_ARRAY);
	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, dm->drawObject->uvedges->id);
		glVertexPointer(2, GL_FLOAT, 0, 0);
	}
	else {
		glVertexPointer(2, GL_FLOAT, 0, dm->drawObject->uvedges->pointer);
	}
	
	GLStates |= GPU_BUFFER_VERTEX_STATE;
}

static int GPU_typesize(int type)
{
	switch (type) {
	case GL_FLOAT:
		return sizeof(float);
	case GL_INT:
		return sizeof(int);
	case GL_UNSIGNED_INT:
		return sizeof(unsigned int);
	case GL_BYTE:
		return sizeof(char);
	case GL_UNSIGNED_BYTE:
		return sizeof(unsigned char);
	default:
		return 0;
	}
}

int GPU_attrib_element_size(GPUAttrib data[], int numdata)
{
	int i, elementsize = 0;

	for (i = 0; i < numdata; i++) {
		int typesize = GPU_typesize(data[i].type);
		if (typesize != 0)
			elementsize += typesize*data[i].size;
	}
	return elementsize;
}

void GPU_interleaved_attrib_setup(GPUBuffer *buffer, GPUAttrib data[], int numdata)
{
	int i;
	int elementsize;
	intptr_t offset = 0;

	for (i = 0; i < MAX_GPU_ATTRIB_DATA; i++) {
		if (attribData[i].index != -1) {
			glDisableVertexAttribArrayARB(attribData[i].index);
		}
		else
			break;
	}
	elementsize = GPU_attrib_element_size(data, numdata);

	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffer->id);
		for (i = 0; i < numdata; i++) {
			glEnableVertexAttribArrayARB(data[i].index);
			glVertexAttribPointerARB(data[i].index, data[i].size, data[i].type,
						 GL_FALSE, elementsize, (void *)offset);
			offset += data[i].size*GPU_typesize(data[i].type);

			attribData[i].index = data[i].index;
			attribData[i].size = data[i].size;
			attribData[i].type = data[i].type;
		}
		attribData[numdata].index = -1;
	}
	else {
		for (i = 0; i < numdata; i++) {
			glEnableVertexAttribArrayARB(data[i].index);
			glVertexAttribPointerARB(data[i].index, data[i].size, data[i].type,
						 GL_FALSE, elementsize, (char *)buffer->pointer + offset);
			offset += data[i].size*GPU_typesize(data[i].type);
		}
	}
}


void GPU_buffer_unbind(void)
{
	int i;

	if (GLStates & GPU_BUFFER_VERTEX_STATE)
		glDisableClientState(GL_VERTEX_ARRAY);
	if (GLStates & GPU_BUFFER_NORMAL_STATE)
		glDisableClientState(GL_NORMAL_ARRAY);
	if (GLStates & GPU_BUFFER_TEXCOORD_STATE)
		glDisableClientState(GL_TEXTURE_COORD_ARRAY);
	if (GLStates & GPU_BUFFER_COLOR_STATE)
		glDisableClientState(GL_COLOR_ARRAY);
	if (GLStates & GPU_BUFFER_ELEMENT_STATE) {
		if (useVBOs) {
			glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
		}
	}
	GLStates &= !(GPU_BUFFER_VERTEX_STATE | GPU_BUFFER_NORMAL_STATE |
	              GPU_BUFFER_TEXCOORD_STATE | GPU_BUFFER_COLOR_STATE |
	              GPU_BUFFER_ELEMENT_STATE);

	for (i = 0; i < MAX_GPU_ATTRIB_DATA; i++) {
		if (attribData[i].index != -1) {
			glDisableVertexAttribArrayARB(attribData[i].index);
		}
		else
			break;
	}

	if (useVBOs)
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
}

/* confusion: code in cdderivedmesh calls both GPU_color_setup and
 * GPU_color3_upload; both of these set the `colors' buffer, so seems
 * like it will just needlessly overwrite? --nicholas */
void GPU_color3_upload(DerivedMesh *dm, unsigned char *data)
{
	if (dm->drawObject == 0)
		dm->drawObject = GPU_drawobject_new(dm);
	GPU_buffer_free(dm->drawObject->colors);

	dm->drawObject->colors = gpu_buffer_setup(dm, dm->drawObject, 3,
						  sizeof(char)*3*dm->drawObject->tot_triangle_point,
						  GL_ARRAY_BUFFER_ARB, data, GPU_buffer_copy_color3);
}

void GPU_color_switch(int mode)
{
	if (mode) {
		if (!(GLStates & GPU_BUFFER_COLOR_STATE))
			glEnableClientState(GL_COLOR_ARRAY);
		GLStates |= GPU_BUFFER_COLOR_STATE;
	}
	else {
		if (GLStates & GPU_BUFFER_COLOR_STATE)
			glDisableClientState(GL_COLOR_ARRAY);
		GLStates &= (!GPU_BUFFER_COLOR_STATE);
	}
}

/* return 1 if drawing should be done using old immediate-mode
 * code, 0 otherwise */
int GPU_buffer_legacy(DerivedMesh *dm)
{
	int test= (U.gameflags & USER_DISABLE_VBO);
	if (test)
		return 1;

	if (dm->drawObject == 0)
		dm->drawObject = GPU_drawobject_new(dm);
	return dm->drawObject->legacy;
}

void *GPU_buffer_lock(GPUBuffer *buffer)
{
	float *varray;

	if (!buffer)
		return 0;

	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffer->id);
		varray = glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
		return varray;
	}
	else {
		return buffer->pointer;
	}
}

void *GPU_buffer_lock_stream(GPUBuffer *buffer)
{
	float *varray;

	if (!buffer)
		return 0;

	if (useVBOs) {
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffer->id);
		/* discard previous data, avoid stalling gpu */
		glBufferDataARB(GL_ARRAY_BUFFER_ARB, buffer->size, 0, GL_STREAM_DRAW_ARB);
		varray = glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
		return varray;
	}
	else {
		return buffer->pointer;
	}
}

void GPU_buffer_unlock(GPUBuffer *buffer)
{
	if (useVBOs) {
		if (buffer) {
			/* note: this operation can fail, could return
			 * an error code from this function? */
			glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);
		}
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
	}
}

/* used for drawing edges */
void GPU_buffer_draw_elements(GPUBuffer *elements, unsigned int mode, int start, int count)
{
	glDrawElements(mode, count, GL_UNSIGNED_INT,
		       (useVBOs ?
			(void*)(start * sizeof(unsigned int)) :
			((int*)elements->pointer) + start));
}


/* XXX: the rest of the code in this file is used for optimized PBVH
 * drawing and doesn't interact at all with the buffer code above */

/* Convenience struct for building the VBO. */
typedef struct {
	float co[3];
	short no[3];
} VertexBufferFormat;

struct GPU_Buffers {
	/* opengl buffer handles */
	GLuint vert_buf, index_buf;
	GLenum index_type;

	/* mesh pointers in case buffer allocation fails */
	MFace *mface;
	MVert *mvert;
	int *face_indices;
	int totface;

	/* grid pointers */
	DMGridData **grids;
	const DMFlagMat *grid_flag_mats;
	const BLI_bitmap *grid_hidden;
	int *grid_indices;
	int totgrid;
	int gridsize;
	int has_hidden;

	unsigned int tot_tri, tot_quad;
};

void GPU_update_mesh_buffers(GPU_Buffers *buffers, MVert *mvert,
			int *vert_indices, int totvert)
{
	VertexBufferFormat *vert_data;
	int i;

	if (buffers->vert_buf) {
		/* Build VBO */
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffers->vert_buf);
		glBufferDataARB(GL_ARRAY_BUFFER_ARB,
		                sizeof(VertexBufferFormat) * totvert,
		                NULL, GL_STATIC_DRAW_ARB);
		vert_data = glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);

		if (vert_data) {
			for (i = 0; i < totvert; ++i) {
				MVert *v = mvert + vert_indices[i];
				VertexBufferFormat *out = vert_data + i;

				copy_v3_v3(out->co, v->co);
				memcpy(out->no, v->no, sizeof(short) * 3);
			}

			glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);
		}
		else {
			glDeleteBuffersARB(1, &buffers->vert_buf);
			buffers->vert_buf = 0;
		}

		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
	}

	buffers->mvert = mvert;
}

GPU_Buffers *GPU_build_mesh_buffers(int (*face_vert_indices)[4],
									MFace *mface, MVert *mvert,
									int *face_indices,
									int totface)
{
	GPU_Buffers *buffers;
	unsigned short *tri_data;
	int i, j, k, tottri;

	buffers = MEM_callocN(sizeof(GPU_Buffers), "GPU_Buffers");
	buffers->index_type = GL_UNSIGNED_SHORT;

	/* Count the number of visible triangles */
	for (i = 0, tottri = 0; i < totface; ++i) {
		const MFace *f = &mface[face_indices[i]];
		if (!paint_is_face_hidden(f, mvert))
			tottri += f->v4 ? 2 : 1;
	}
	
	if (GLEW_ARB_vertex_buffer_object && !(U.gameflags & USER_DISABLE_VBO))
		glGenBuffersARB(1, &buffers->index_buf);

	if (buffers->index_buf) {
		/* Generate index buffer object */
		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, buffers->index_buf);
		glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB,
		                sizeof(unsigned short) * tottri * 3, NULL, GL_STATIC_DRAW_ARB);

		/* Fill the triangle buffer */
		tri_data = glMapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
		if (tri_data) {
			for (i = 0; i < totface; ++i) {
				const MFace *f = mface + face_indices[i];
				int v[3];

				/* Skip hidden faces */
				if (paint_is_face_hidden(f, mvert))
					continue;

				v[0]= 0;
				v[1]= 1;
				v[2]= 2;

				for (j = 0; j < (f->v4 ? 2 : 1); ++j) {
					for (k = 0; k < 3; ++k) {
						*tri_data = face_vert_indices[i][v[k]];
						++tri_data;
					}
					v[0] = 3;
					v[1] = 0;
					v[2] = 2;
				}
			}
			glUnmapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB);
		}
		else {
			glDeleteBuffersARB(1, &buffers->index_buf);
			buffers->index_buf = 0;
		}

		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
	}

	if (buffers->index_buf)
		glGenBuffersARB(1, &buffers->vert_buf);

	buffers->tot_tri = tottri;

	buffers->mface = mface;
	buffers->face_indices = face_indices;
	buffers->totface = totface;

	return buffers;
}

void GPU_update_grid_buffers(GPU_Buffers *buffers, DMGridData **grids,
	const DMFlagMat *grid_flag_mats, int *grid_indices, int totgrid, int gridsize)
{
	DMGridData *vert_data;
	int i, j, k, totvert;

	totvert= gridsize*gridsize*totgrid;

	/* Build VBO */
	if (buffers->vert_buf) {
		int smooth = grid_flag_mats[grid_indices[0]].flag & ME_SMOOTH;

		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffers->vert_buf);
		glBufferDataARB(GL_ARRAY_BUFFER_ARB,
		                sizeof(DMGridData) * totvert,
		                NULL, GL_STATIC_DRAW_ARB);
		vert_data = glMapBufferARB(GL_ARRAY_BUFFER_ARB, GL_WRITE_ONLY_ARB);
		if (vert_data) {
			for (i = 0; i < totgrid; ++i) {
				DMGridData *grid= grids[grid_indices[i]];
				memcpy(vert_data, grid, sizeof(DMGridData)*gridsize*gridsize);

				if (!smooth) {
					/* for flat shading, recalc normals and set the last vertex of
					 * each quad in the index buffer to have the flat normal as
					 * that is what opengl will use */
					for (j = 0; j < gridsize-1; ++j) {
						for (k = 0; k < gridsize-1; ++k) {
							float fno[3];
							normal_quad_v3(fno,
								grid[(j+1)*gridsize + k].co,
								grid[(j+1)*gridsize + k+1].co,
								grid[j*gridsize + k+1].co,
								grid[j*gridsize + k].co);

							copy_v3_v3(vert_data[(j+1)*gridsize + (k+1)].no, fno);
						}
					}
				}

				vert_data += gridsize*gridsize;
			}
			glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);
		}
		else {
			glDeleteBuffersARB(1, &buffers->vert_buf);
			buffers->vert_buf = 0;
		}
		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
	}

	buffers->grids = grids;
	buffers->grid_indices = grid_indices;
	buffers->totgrid = totgrid;
	buffers->gridsize = gridsize;
	buffers->grid_flag_mats = grid_flag_mats;

	//printf("node updated %p\n", buffers);
}

/* Returns the number of visible quads in the nodes' grids. */
static int gpu_count_grid_quads(BLI_bitmap *grid_hidden,
								int *grid_indices, int totgrid,
								int gridsize)
{
	int gridarea = (gridsize-1) * (gridsize-1);
	int i, x, y, totquad;

	/* grid hidden layer is present, so have to check each grid for
	 * visiblity */

	for (i = 0, totquad = 0; i < totgrid; i++) {
		const BLI_bitmap gh = grid_hidden[grid_indices[i]];

		if (gh) {
			/* grid hidden are present, have to check each element */
			for (y = 0; y < gridsize-1; y++) {
				for (x = 0; x < gridsize-1; x++) {
					if (!paint_is_grid_face_hidden(gh, gridsize, x, y))
						totquad++;
				}
			}
		}
		else
			totquad += gridarea;
	}

	return totquad;
}

/* Build the element array buffer of grid indices using either
 * unsigned shorts or unsigned ints. */
#define FILL_QUAD_BUFFER(type_, tot_quad_, buffer_)                     \
	{                                                                   \
		type_ *quad_data;                                               \
		int offset = 0;                                                 \
		int i, j, k;                                                    \
		                                                                \
		glBufferDataARB(GL_ELEMENT_ARRAY_BUFFER_ARB,                    \
						sizeof(type_) * (tot_quad_) * 4, NULL,          \
						GL_STATIC_DRAW_ARB);                            \
		                                                                \
		/* Fill the quad buffer */                                      \
		quad_data = glMapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB,         \
								   GL_WRITE_ONLY_ARB);                  \
		if (quad_data) {                                                \
			for (i = 0; i < totgrid; ++i) {								\
				BLI_bitmap gh = NULL;									\
				if (grid_hidden)										\
					gh = grid_hidden[(grid_indices)[i]];				\
																		\
				for (j = 0; j < gridsize-1; ++j) {                      \
					for (k = 0; k < gridsize-1; ++k) {                  \
						/* Skip hidden grid face */						\
						if (gh &&										\
						   paint_is_grid_face_hidden(gh,				\
													 gridsize, k, j))	\
							continue;									\
																		\
						*(quad_data++)= offset + j*gridsize + k+1;      \
						*(quad_data++)= offset + j*gridsize + k;        \
						*(quad_data++)= offset + (j+1)*gridsize + k;    \
						*(quad_data++)= offset + (j+1)*gridsize + k+1;  \
					}                                                   \
				}                                                       \
																		\
				offset += gridsize*gridsize;                            \
			}                                                           \
			glUnmapBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB);              \
		}                                                               \
		else {                                                          \
			glDeleteBuffersARB(1, &(buffer_));							\
			(buffer_) = 0;												\
		}                                                               \
	}
/* end FILL_QUAD_BUFFER */

static GLuint gpu_get_grid_buffer(int gridsize, GLenum *index_type, unsigned *totquad)
{
	static int prev_gridsize = -1;
	static GLenum prev_index_type = 0;
	static GLuint buffer = 0;
	static unsigned prev_totquad;

	/* used in the FILL_QUAD_BUFFER macro */
	const BLI_bitmap *grid_hidden = NULL;
	int *grid_indices = NULL;
	int totgrid = 1;

	/* VBO is disabled; delete the previous buffer (if it exists) and
	 * return an invalid handle */
	if (!GLEW_ARB_vertex_buffer_object || (U.gameflags & USER_DISABLE_VBO)) {
		if (buffer)
			glDeleteBuffersARB(1, &buffer);
		return 0;
	}

	/* VBO is already built */
	if (buffer && prev_gridsize == gridsize) {
		*index_type = prev_index_type;
		*totquad = prev_totquad;
		return buffer;
	}

	/* Build new VBO */
	glGenBuffersARB(1, &buffer);
	if (buffer) {
		*totquad= (gridsize-1)*(gridsize-1);

		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, buffer);

		if (gridsize * gridsize < USHRT_MAX) {
			*index_type = GL_UNSIGNED_SHORT;
			FILL_QUAD_BUFFER(unsigned short, *totquad, buffer);
		}
		else {
			*index_type = GL_UNSIGNED_INT;
			FILL_QUAD_BUFFER(unsigned int, *totquad, buffer);
		}

		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
	}

	prev_gridsize = gridsize;
	prev_index_type = *index_type;
	prev_totquad = *totquad;
	return buffer;
}

GPU_Buffers *GPU_build_grid_buffers(int *grid_indices, int totgrid,
									BLI_bitmap *grid_hidden, int gridsize)
{
	GPU_Buffers *buffers;
	int totquad;
	int fully_visible_totquad = (gridsize-1) * (gridsize-1) * totgrid;

	buffers = MEM_callocN(sizeof(GPU_Buffers), "GPU_Buffers");
	buffers->grid_hidden = grid_hidden;
	buffers->gridsize = gridsize;
	buffers->totgrid = totgrid;

	/* Count the number of quads */
	totquad= gpu_count_grid_quads(grid_hidden, grid_indices, totgrid, gridsize);

	if (totquad == fully_visible_totquad) {
		buffers->index_buf = gpu_get_grid_buffer(gridsize, &buffers->index_type, &buffers->tot_quad);
		buffers->has_hidden = 0;
	}
	else if (GLEW_ARB_vertex_buffer_object && !(U.gameflags & USER_DISABLE_VBO)) {
		/* Build new VBO */
		glGenBuffersARB(1, &buffers->index_buf);
		if (buffers->index_buf) {
			buffers->tot_quad= totquad;

			glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, buffers->index_buf);

			if (totgrid * gridsize * gridsize < USHRT_MAX) {
				buffers->index_type = GL_UNSIGNED_SHORT;
				FILL_QUAD_BUFFER(unsigned short, totquad, buffers->index_buf);
			}
			else {
				buffers->index_type = GL_UNSIGNED_INT;
				FILL_QUAD_BUFFER(unsigned int, totquad, buffers->index_buf);
			}

			glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);
		}

		buffers->has_hidden = 1;
	}

	/* Build coord/normal VBO */
	if (buffers->index_buf)
		glGenBuffersARB(1, &buffers->vert_buf);

	return buffers;
}

#undef FILL_QUAD_BUFFER

static void gpu_draw_buffers_legacy_mesh(GPU_Buffers *buffers, int smooth)
{
	const MVert *mvert = buffers->mvert;
	int i, j;

	for (i = 0; i < buffers->totface; ++i) {
		MFace *f = buffers->mface + buffers->face_indices[i];
		int S = f->v4 ? 4 : 3;
		unsigned int *fv = &f->v1;

		if (paint_is_face_hidden(f, buffers->mvert))
			continue;

		glBegin((f->v4)? GL_QUADS: GL_TRIANGLES);

		if (smooth) {
			for (j = 0; j < S; j++) {
				glNormal3sv(mvert[fv[j]].no);
				glVertex3fv(mvert[fv[j]].co);
			}
		}
		else {
			float fno[3];

			/* calculate face normal */
			if (f->v4) {
				normal_quad_v3(fno, mvert[fv[0]].co, mvert[fv[1]].co,
							   mvert[fv[2]].co, mvert[fv[3]].co);
			}
			else
				normal_tri_v3(fno, mvert[fv[0]].co, mvert[fv[1]].co, mvert[fv[2]].co);
			glNormal3fv(fno);
			
			for (j = 0; j < S; j++)
				glVertex3fv(mvert[fv[j]].co);
		}
		
		glEnd();
	}
}

static void gpu_draw_buffers_legacy_grids(GPU_Buffers *buffers, int smooth)
{
	int i, j, x, y, gridsize = buffers->gridsize;

	for (i = 0; i < buffers->totgrid; ++i) {
		int g = buffers->grid_indices[i];
		const DMGridData *grid = buffers->grids[g];
		BLI_bitmap gh = buffers->grid_hidden[g];

		/* TODO: could use strips with hiding as well */

		if (gh) {
			glBegin(GL_QUADS);
			
			for (y = 0; y < gridsize-1; y++) {
				for (x = 0; x < gridsize-1; x++) {
					const DMGridData *e[4] = {
						&grid[y*gridsize + x],
						&grid[(y+1)*gridsize + x],
						&grid[(y+1)*gridsize + x+1],
						&grid[y*gridsize + x+1]
					};

					/* skip face if any of its corners are hidden */
					if (paint_is_grid_face_hidden(gh, gridsize, x, y))
						continue;

					if (smooth) {
						for (j = 0; j < 4; j++) {
							glNormal3fv(e[j]->no);
							glVertex3fv(e[j]->co);
						}
					}
					else {
						float fno[3];
						normal_quad_v3(fno, e[0]->co, e[1]->co, e[2]->co, e[3]->co);
						glNormal3fv(fno);

						for (j = 0; j < 4; j++)
							glVertex3fv(e[j]->co);
					}
				}
			}

			glEnd();
		}
		else if (smooth) {
			for (y = 0; y < gridsize-1; y++) {
				glBegin(GL_QUAD_STRIP);
				for (x = 0; x < gridsize; x++) {
					const DMGridData *a = &grid[y*gridsize + x];
					const DMGridData *b = &grid[(y+1)*gridsize + x];

					glNormal3fv(a->no);
					glVertex3fv(a->co);
					glNormal3fv(b->no);
					glVertex3fv(b->co);
				}
				glEnd();
			}
		}
		else {
			for (y = 0; y < gridsize-1; y++) {
				glBegin(GL_QUAD_STRIP);
				for (x = 0; x < gridsize; x++) {
					const DMGridData *a = &grid[y*gridsize + x];
					const DMGridData *b = &grid[(y+1)*gridsize + x];

					if (x > 0) {
						const DMGridData *c = &grid[y*gridsize + x-1];
						const DMGridData *d = &grid[(y+1)*gridsize + x-1];
						float fno[3];
						normal_quad_v3(fno, d->co, b->co, a->co, c->co);
						glNormal3fv(fno);
					}

					glVertex3fv(a->co);
					glVertex3fv(b->co);
				}
				glEnd();
			}
		}
	}
}

void GPU_draw_buffers(GPU_Buffers *buffers, DMSetMaterial setMaterial)
{
	int smooth = 0;

	if (buffers->totface) {
		const MFace *f = &buffers->mface[buffers->face_indices[0]];
		if (!setMaterial(f->mat_nr + 1, NULL))
			return;

		smooth = f->flag & ME_SMOOTH;
		glShadeModel(smooth ? GL_SMOOTH: GL_FLAT);
	}
	else if (buffers->totgrid) {
		const DMFlagMat *f = &buffers->grid_flag_mats[buffers->grid_indices[0]];
		if (!setMaterial(f->mat_nr + 1, NULL))
			return;

		smooth = f->flag & ME_SMOOTH;
		glShadeModel(smooth ? GL_SMOOTH: GL_FLAT);
	}

	if (buffers->vert_buf && buffers->index_buf) {
		glEnableClientState(GL_VERTEX_ARRAY);
		glEnableClientState(GL_NORMAL_ARRAY);

		glBindBufferARB(GL_ARRAY_BUFFER_ARB, buffers->vert_buf);
		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, buffers->index_buf);

		if (buffers->tot_quad) {
			unsigned offset = 0;
			int i, last = buffers->has_hidden ? 1 : buffers->totgrid;
			for (i = 0; i < last; i++) {
				glVertexPointer(3, GL_FLOAT, sizeof(DMGridData), offset + (char*)offsetof(DMGridData, co));
				glNormalPointer(GL_FLOAT, sizeof(DMGridData), offset + (char*)offsetof(DMGridData, no));
				
				glDrawElements(GL_QUADS, buffers->tot_quad * 4, buffers->index_type, 0);

				offset += buffers->gridsize * buffers->gridsize * sizeof(DMGridData);
			}
		}
		else {
			glVertexPointer(3, GL_FLOAT, sizeof(VertexBufferFormat), (void*)offsetof(VertexBufferFormat, co));
			glNormalPointer(GL_SHORT, sizeof(VertexBufferFormat), (void*)offsetof(VertexBufferFormat, no));

			glDrawElements(GL_TRIANGLES, buffers->tot_tri * 3, buffers->index_type, 0);
		}

		glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);
		glBindBufferARB(GL_ELEMENT_ARRAY_BUFFER_ARB, 0);

		glDisableClientState(GL_VERTEX_ARRAY);
		glDisableClientState(GL_NORMAL_ARRAY);
	}
	/* fallbacks if we are out of memory or VBO is disabled */
	else if (buffers->totface) {
		gpu_draw_buffers_legacy_mesh(buffers, smooth);
	}
	else if (buffers->totgrid) {
		gpu_draw_buffers_legacy_grids(buffers, smooth);
	}
}

void GPU_free_buffers(GPU_Buffers *buffers)
{
	if (buffers) {
		if (buffers->vert_buf)
			glDeleteBuffersARB(1, &buffers->vert_buf);
		if (buffers->index_buf && (buffers->tot_tri || buffers->has_hidden))
			glDeleteBuffersARB(1, &buffers->index_buf);

		MEM_freeN(buffers);
	}
}